Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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Using a Public-Key-Encryption browser side to avoid PCI compliance

We're developing a web application in which certain not logged users (clients) need to send their credit card details to other users (merchants) - which, we'll assume, are PCI compliant. We are ...
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1answer
45 views

Uniqueness of name in cryptography

If I publish my public key (I think I understand how this works, I'm still learning encryption) and I have a common name, could this leas to problems at all? OR does the email part guarantee that this ...
37
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1answer
3k views

How does a SIM card prevent cloning?

I have read a few articles about SIM cards, stating that the chip inside them uses some cryptographic magic to prevent people from cloning your number. This to me seems borderline impossible, given ...
2
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2answers
76 views

Related-password hash security

Say we are given a strong cryptographic hash function hash(), a strong completely random password of 15 characters pass15, two single-character salt values salta, saltb. We compute the hashes hasha, ...
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2answers
2k views

openssl_digest vs hash vs hash_hmac? Difference between SALT & HMAC?

openssl_digest vs hash vs hash_hmac I want to use SHA512 for storing password. Which of the above methods are best to use? Why? What is the difference between SALT & HMAC? I just read ...
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3answers
282 views

How does encryption/decryption work when one generate random key?

I am new to this and want to ask a basic question. Suppose I used my password (say "ABC123") to generate a key using the PBKDF2 algorithm (or any such algorithm). For encrypting a file I'll input my ...
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4answers
2k views

What are the chances to generate the same ssh key?

I could generate ssh keys on the client like (without password): ssh-keygen -b 8192 -t rsa -f /home/THEUSER/.ssh/id_rsa -P '' -v and copy the generated id_rsa.pub to the server: ssh-copy-id -i ...
2
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1answer
87 views

How does signing work with Elliptic Curve Crypto?

So I have read up and have a decent understanding of how the crypto works with Elliptic Curve Cryptography. I also think I have an understanding of how signing works with things like Elliptic Curve ...
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2answers
60 views

Is there something similar to pseudorandom generators but in the opposite direction?

Pseudorandom generators (PRG) are functions that takes a random small input (called the Seed) and maps it into much larger output . However, the mapping process must be unpredictable in order for the ...
2
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1answer
157 views

adding certificate that resides on smartcard to the microsoft store with private key ownership

how can we solve CryptAcquireCertificatePrivateKey fails with 0x8009200B when adding certificate from smartcard to local user store? in an enrollment system where users generate smartcard certificate ...
0
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2answers
66 views

How to generate a superkey to decrypt strings

I'm working on an application where users have a key or password generated by me that is used to encrypt a string. Each user has their personal key, and no user should be able to decrypt another ...
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1answer
81 views

How easy is it to crack this encryption algorithm? [closed]

When I was about 13 or 14 years old, I was a little interested in cryptography (which is, after all, an interesting field). I learnt quite a lot since that time (it has been about 8 years since then), ...
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1answer
28 views

Can any ECC field element be safely serialized as “compressed” and then restored as uncompressed?

I have a library that stores all its ECC Field Elements in uncompressed form, in a bloated Base64 XML format, and storage has become a concern. (We want to support QR code as a form factor,etc) ...
22
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6answers
18k views

Most secure password hash algorithm(s)?

What is/are currently the most cryptographically secure hashing algorithm(s)? (available in PHP) Speed is irrelevant, because I'm iterating the hash over a fixed time (rather than a fixed number of ...
38
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5answers
5k views

Why shouldn't we roll our own?

Why shouldn't we create our own security schemes? I see a lot of questions around here about custom crypto and custom security mechanisms, especially around password hashing. With that in mind, I'm ...
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3answers
102 views

Java AES encryption output length

I am trying to encrypt few database columns (string values) using Java AES algorithm. This is to protect certain sensitive data. For some users these data should decrypted. In Java AES encryption, if ...
2
votes
2answers
81 views

What problem does ECC seek to fix compared to RSA?

Elliptical Curve Cryptography (ECC) is one of the newest encryption schemes to challenge RSA cryptography. What problem does ECC seek to fix compared to RSA? Would you have any qualms with using ECC ...
177
votes
7answers
126k views

RSA vs. DSA for SSH authentication keys

When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type). What is the difference between RSA and DSA ...
2
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1answer
53 views

Would it be possible to add additional files to a password protected zip 2.0 file

So the scenario is this: I don't have the ability to determine/recover the master password for a production system that uses zip 2 archives. However, I need to be able to add new files to existing ...
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1answer
22 views

In TLS1.2 AES-GCM mode, what happened when input is not exactly the multiple of its block size?

I know that AES-GCM mode does not need padding, and its output are exactly the length of input data plus the tagging. But I am a little bit lost, as AES itself is block cipher, it could only operate ...
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2answers
77 views

Cryptography protocol suitable for two-way radio communications

Specifically talking about walkie talkie radio networks. Suppose there is a group of up to 16 persons, each equipped with such a unit. Typically, one person will be talking with one another ...
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2answers
83 views

Some questions about crypto

How to determine what type of encoding/encryption has been used? This link discusses in the first answer a "128 bit" value. How do you know that it is 128-bit and what is a 128bit value? If I md5sum ...
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1answer
83 views

good books for learning network and web security? [closed]

I am reading "Hacking The Art of Exploitation" book . i have read till chapter 2 programming but most of it has gone above my head . I want to learn basically cryptography , network security and web ...
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1answer
167 views

Requiring 2 keys to access a content

I need to use an external service that can only be accessed by password. I don't like the idea of storing the plaintext password on the server, but AFAIK there's not much I can do. Considering this ...
0
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2answers
55 views

What is the collision likelihood of MD5 when non-numeric values are removed?

Start with a unique identifier String macAddress = "CC:3A:61:24:D6:96"; Hash the identifier via MD5 implementation String hash = md5(macAddress); //bd37f780e10244cf28810b969559ad5b Remove all ...
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0answers
20 views

Mobile App Processing Debit Card Transactions

I am creating a mobile app for iPhone and Android and the respective API that will be exposed to support the operations. This operations will require the customer to type the PIN to complete the ...
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1answer
27 views

Сompromised client.p12 file in OpenVPN

I'm not clearly understand technologies behind OpenVPN, so I have a question about OpenVPN security: What if I have client.p12 (PKCS#12) file and this file was leaked (with export password) to some ...
2
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1answer
79 views

Properties of AES Encryption

First of all, I apologize if these questions can be answered using a web search, but I'm sort of a crypto noob and don't know what to search for. Given N AES encrypted messages (where the message ...
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vote
1answer
31 views

What is the relationship between Suite B and FIPS 140-2?

What is the relationship between the Suite B algorithms and FIPS 140-2 certification? Does OpenSSL meet both criteria? From what I've read, it seems that OpenSSL's crypto library implements many ...
2
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1answer
58 views

X509Certificate - How to set validation Policies?

I have an X509Certificate (say Certificate-A) for signing purpose. While validating this certificate, I have to check its path with Intermediate & Root certificate which I have implemented fully. ...
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2answers
240 views

What's the point of the nonce in CTR mode?

Does having a nonce in CTR mode actually improve security (vs. just using 1, 2, 3, etc. - basically a constant nonce of 0)? As far as I can tell, the best-case scenario security-wise is that the ...
5
votes
3answers
108 views

AES256, repeated IVs and mostly-costant payload: how ok/bad is that?

I recently came across an application that more or less does this: starts from a (supposedly unknown to others) key generates a random IV encrypts some smallish (~ 160 bytes) payload with the key ...
3
votes
1answer
94 views

When to use HMAC alongside AES?

One of my clients wants to provide an URL to each of his customers to register in a system. This URL would contain a query string parameter with some data (e.g. code, email and name) from his clients ...
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2answers
187 views

Alternative for cryptography

Is there any alternative for cryptography? I heard a lot about quantum cryptography, but is this the only stuff which have a chance to exist in the future? Are there any other kinds of cryptography?
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2answers
153 views

Reversible Hash Function?

Is there any reversible hash function? The hash function like SHA and MD5 are not reversible. I would like to know if there exist some reversible hash functions?
0
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0answers
47 views

How to secure my REST API once user authenticates with Google on mobile client?

In my application, I build REST APIs so that user can interact with my application server. Since I do not want to maintain User/Passwords, my iOS app authenticates client using Google. This all ...
3
votes
1answer
50 views

What crypto prevents & detects “invisible” CAs? (e.g. in X509v4)

For this question, I'm calling an "invisible CA" one that Is signed by a root ca and exists as a 2nd or 3rd tier Is valid, not expired or revoked Has a different Public key than one that is ...
0
votes
1answer
60 views

Linux SSH and GPG

Can anyone please give me a quick crash course on SSH and GPG? SSH: What is the difference between public and private keys? Should I back up my ~/.ssh/ directory, what are the security implications ...
0
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0answers
21 views

How does OTR's authentication using “Question and answer” protect against MiTM?

I've read that the answer has something to do Socialist Millionaire, but I still don't understand how can the user be protected against malicious Man In The Middle, which would capture the question ...
13
votes
2answers
3k views

What should I know before configuring Perfect Forward Secrecy?

PFS has gained attention in our audit department because of its innate ability to limit our exposure if someone steals our private key. What pitfalls or common mistakes should I be aware of before ...
0
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2answers
56 views

What are the alternatives to ECDSA for an authentication protocol?

In an authentication protocol, S has a public/private key pair known to C, and S and C have established a secure channel (for example, using DH or ECDH, or any other key exchange protocol). C wishes ...
3
votes
1answer
225 views

Open source solution to capture and decrypt SSH traffic (with private key)?

I am looking for a free open source solution that is able to capture and decrypt SSH traffic given the fact that I can provide the server's RSA private key (something like SSH CryptoAuditor). Please ...
0
votes
1answer
34 views

Publicly Available API + Sensitive ID/Key Transmission Over HTTP

I've run into a predicament... I'm developing a mobile application that utilizes a server for various things. One portion is that it stores an id/key pair related to accessing and processing ...
2
votes
1answer
90 views

Bastion host that allows jailed users to SSH but protects private key

Basically, I'm trying to let the user use a private key without having read access to it. Use case: Employee needs to SSH to a server in the data center. There is 1 private key for all servers, ...
1
vote
1answer
173 views

Is my AES/CTR/RIPEMD encryption correctly implemented?

Below is my encryption implementation in PHP. It's based on mcrypt, and uses AES-128 in CTR mode along with a RIPEMD-128 HMAC for integrity checking. For brevity, I've inlined the functions for ...
7
votes
6answers
5k views

How would one fully protect himself against man in the middle-attacks?

Imagine I have a computer where all the trafic is being sent through the MitM. How would it be possible to have a secure connection through this setup? In this case it would be OK to design a new ...
1
vote
0answers
35 views

Generate a public key certificate signed by CA with OpenSSL [migrated]

I am working on a webservice that requires a signature in the sent and received messages. After sending a certificate request to the entity that will consume the webservice, they sent me (in addition ...
0
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1answer
98 views

Advice on using encryption and hashing

I'm going to rephrase a question I asked earlier, as I don't think anyone understood what I meant. Bascially I'm writting a web based password locker, which can have multiple accounts; so that users ...
0
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1answer
59 views

Securing a Shuffle Algorithm

After reading about writing a secure shuffle algorithm, I realized that my module that generates a password is only as strong as my PRNG, which in this case is Math.random(). I'm confused as to how to ...
0
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1answer
57 views

Using encryption and hashing

I'm writing a project to securely store and share passwords between users, I've been doing tons of research into encryption algorithms, CSPRNGs, hashing algorithms, key stretching etc... I just want ...